Having high blood pressure (hypertension) during pregnancy — whether you develop the condition before or after conception — requires special care. Here's what you need to know about high blood pressure and pregnancy.

Sometimes high blood pressure is present before pregnancy. In other cases, high blood pressure develops during pregnancy. For example:

Gestational hypertension. Women with gestational hypertension have high blood pressure that develops after 20 weeks of pregnancy. There is no excess protein in the urine or other signs of organ damage. Some women with gestational hypertension eventually develop preeclampsia.

Chronic hypertension. Chronic hypertension is high blood pressure that was present before pregnancy or that occurs before 20 weeks of pregnancy. But because high blood pressure usually doesn't have symptoms, it might be hard to determine when it began.

Chronic hypertension with superimposed preeclampsia. This condition occurs in women with chronic high blood pressure before pregnancy who then develop worsening high blood pressure and protein in the urine or other health complications during pregnancy.

Preeclampsia. Sometimes chronic hypertension or gestational hypertension leads to preeclampsia, a pregnancy complication characterized by high blood pressure and signs of damage to another organ system — usually after 20 weeks of pregnancy. Left untreated, preeclampsia can lead to serious — even fatal — complications for mother and baby. Previously, preeclampsia was only diagnosed if a pregnant woman had high blood pressure and protein in her urine. However, experts now know that it's possible to have preeclampsia, yet never have protein in the urine.

High blood pressure during pregnancy poses various risks, including:

Decreased blood flow to the placenta. If the placenta doesn't get enough blood, your baby might receive less oxygen and fewer nutrients. This can lead to slow growth, low birth weight or preterm birth. Prematurity can lead to breathing problems for the baby.

Placental abruption. Preeclampsia increases your risk of placental abruption, in which the placenta separates from the inner wall of your uterus before delivery. Severe abruption can cause heavy bleeding and damage to the placenta, which can be life-threatening for both you and your baby.

Premature delivery. Sometimes an early delivery is needed to prevent potentially life-threatening complications.

Future cardiovascular disease. Having preeclampsia increases your risk of future heart and blood vessel (cardiovascular) disease. The risk is even greater if you've had preeclampsia more than once or you've had a premature birth. To minimize this risk, after delivery try to maintain your ideal weight, eat a variety of fruits and vegetables, exercise regularly, and don't smoke.

Preeclampsia sometimes develops without any symptoms. High blood pressure might develop slowly, but more commonly it has a sudden onset. Monitoring your blood pressure is an important part of prenatal care because the first sign of preeclampsia is commonly a rise in blood pressure. Blood pressure that is 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least four hours apart — is abnormal.

Changes in vision, including temporary loss of vision, blurred vision or light sensitivity

Upper abdominal pain, usually under your ribs on the right side

Nausea or vomiting

Decreased urine output

Decreased levels of platelets in your blood (thrombocytopenia)

Impaired liver function

Shortness of breath, caused by fluid in your lungs

Sudden weight gain and swelling (edema) — particularly in your face and hands — often accompanies preeclampsia. But these things also occur in many normal pregnancies, so they're not considered reliable signs of preeclampsia.

Any medication you take during pregnancy can affect your baby. Although some medications used to lower blood pressure are considered safe during pregnancy, others — such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and renin inhibitors — are generally avoided during pregnancy.

Treatment is important, however. The risk of heart attack, stroke and other problems associated with high blood pressure doesn't go away during pregnancy. And high blood pressure can be dangerous for your baby, too.

If you need medication to control your blood pressure during pregnancy, your health care provider will prescribe the safest medication at the most appropriate dose. Take the medication exactly as prescribed. Don't stop taking the medication or adjust the dose on your own.

If you have high blood pressure, schedule a preconception appointment with the health care provider who'll be handling your pregnancy. Also meet with other members of your health care team, such as your family doctor or cardiologist. They'll evaluate how well you're managing your high blood pressure and consider any treatment changes you might need to make before pregnancy. If you're overweight, your health care provider might recommend losing the excess pounds before you try to conceive.

During pregnancy, you'll see your health care provider often. Your weight and blood pressure will be checked at every visit, and you might need frequent blood and urine tests.

Researchers continue to study ways to prevent preeclampsia, but so far, no clear strategies have emerged. If you had preeclampsia in a previous pregnancy that resulted in delivery before 34 weeks' gestation or you had preeclampsia in more than one previous pregnancy, your doctor might recommend a daily low-dose aspirin — between 60 and 81 milligrams — beginning late in your first trimester.

Your health care provider might suggest inducing labor a few days before your due date to avoid complications. If you develop preeclampsia or other complications, induction might be needed even earlier. If you have severe preeclampsia, you might be given medication during labor to help prevent seizures. In some cases, a C-section might be needed.

Breast-feeding is encouraged for most women who have high blood pressure, even those who take medication. Discuss any medication adjustments you'll need to make with your health care provider ahead of time. Sometimes an alternate blood pressure medication is recommended. Your health care provider might also recommend that you avoid breast-feeding right after you take your medication.

References

High blood pressure in pregnancy. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/public/heart/hbp/hbp_preg.htm. Accessed May 27, 2014.

Frequently asked questions. Pregnancy FAQ034. High blood pressure during pregnancy. American College of Obstetricians and Gynecologists. http://www.acog.org/~/media/For%20Patients/faq034.pdf?dmc=1&ts=20140527T1327147767. Accessed May 27, 2014.

Hypertension in pregnancy. Washington, D.C.: American College of Obstetricians and Gynecologists. 2013. http://www.acog.org/Resources_And_Publications/Task_Force_and_Work_Group_Reports/Hypertension_in_Pregnancy. Accessed May 27, 2014.

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